


Not as Planned

by Elsewhat999



Category: Underfell - Fandom, Undertale (Video Game)
Genre: Domestic Fluff, F/M, Female Reader, Fluff, Menstruation, No period sex, Periods, Reader has a vagina, explanation of human reproduction to a Monster, might add a sex scene in chapter two, sans/reader - Freeform
Language: English
Status: Completed
Published: 2017-12-10
Updated: 2017-12-10
Packaged: 2019-02-12 22:20:54
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,201
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12969630
Author URL: https://archiveofourown.org/users/Elsewhat999/pseuds/Elsewhat999
Summary: Sans' plan to wake you up with some lazy morning sex goes awry.





	Not as Planned

You hummed contentedly as you woke to Sans wrapping his arms around you and pulling you closer to him. 

“You awake doll?” He growled softly into your ear, pressing himself against you, his hard cock pressing against your ass in a most agreeable way. 

“Mm, yeah.” You murmured, pressing back against him, keeping your eyes closed. 

There was a dull ache in your lower stomach, but you ignored it. It wasn’t enough to stop you from warming up to his advances. 

“Again?” You teased as his hand went lower on your stomach, slipping into your panties. 

Layla moaned softly as he gently traced your folds before petting softly at your clit. 

“Yer one ta talk.” He chuckled, “Feel how wet ya are.” 

“Easy.” You whispered, wincing slightly. Your sex was sore. Sans and you had fairly rough sex last night, it was true, but you shouldn’t be sore because of that. You usually weren’t. 

“You okay, doll?” He asked, concern in his voice as he stopped his touching, beginning to withdraw his hand. 

“Yeah, I’m just sore.” You said, sitting up and rubbing your eyes. 

“__y/n__?” His voice made you turn to look at him. He sounded…scared? “__y/n__, what did I do?” 

There was blood on his phalanges and he was looking at you with horror on his face. 

“Oh, shit.” You hissed, yanked the thin sheet away from yourself to see blood streaked on your thighs, the crotch on your pink panties soaked to a deep maroon. 

“Shit, __y/n__. Don’t move, okay? I’ll get-I’ll get-“ He started to get up, but you grabbed his hand and stopped him. 

“Sans, I need you to calm down for me.” You told him, pulling him closer to you. “You did not hurt me. I am not hurt.” You told him firmly, pressing a kiss to his forehead. “What is happening to me right this moment is something that happens to me a few times a year. It’s part of the human reproduction system.” You did not want to have to give your Monster boyfriend a lesson in human biology, but it was obvious you would have to. “I have an organ called a uterus. Many human women have this organ. It’s the female reproductive organ. It’s connected to something called ovaries. Ovaries produce eggs which then travel through fallopian tubes into the uterus where it attaches to the uterine lining. If sperm is introduced, that egg can develop into a baby. If not, the lining it is attached too, as well as the egg, is expelled from the uterus in the form of…blood. Usually, this happens to women about once a month. However, I am on a medication causes it too to happen about once every four months. Do you understand?” You asked, holding on to him. You hoped that if nothing else, your explanation would keep him from pelting off to call 911 or something. 

“So. Ya ain’t hurt?” He asked, his voice was shaky as he took your hands. 

“No. I’m in a little bit of discomfort. The blood doesn’t just flow out, muscles contract to push it out and that hurts a little bit, but it’s not bad right now-“ 

“But it can get bad?” 

“Sometimes, but I’m used to it.” You told him with a shrug. It was true, you had suffered severe cramps when you were younger, it was why you had started taking the medication in the first place. And the meds did help, but they didn’t stop the cramping or assorted side effects completely. 

“Shit __y/n__, that is horrible.” He said with feeling and you laughed quietly. 

“You have no idea, Sans. You have no idea.” You told him, kissing him softly and standing. 

You winced at the mess you made of the sheets and hoped the blood hadn’t stained the mattress. 

“Go get yaself cleaned up, Doll. I’ll take care of things in here.” He told you when you started pulling the sheets off the bed. 

“Thanks babe.” You told him sincerely, kissing the top of his skull. 

Sans smiled distracted at you as he yanked the sheets off the bed. 

After a hot shower, you dressed again in a clean tanktop, underwear and a pad and sweat pants. You weren’t going anywhere today, might as well stay in your pajamas.

You always got so sore while you were on her period, you could almost never use Tampons, something you had been teased about on occasion by your female coworkers. 

You went back into the bedroom, pulling your wet hair over your shoulder to see the bed freshly made with clean sheets and your boyfriend, usually surly and tsundere waiting for you with a bouquet of flowers, lily of the valley, irises and bluebells, all of you favorite flowers, and a box of chocolate. 

A soft laugh escaped you and kissed him on the cheek. “Oh, Sans. Thank you. How’d you get all that done in such a short amount of time?” You asked him, taking the flowers from him and burying face face in them and inhaling deeply. They smelled amazing. 

“Magic.” He said with a grin, “Internet says I should be sweet to ya while this is happenin’. Got you flowers and chocolates.” Sans sounded immensely proud of himself. 

“My sweet boy. Thank you.” You teased gently, pressing kisses against the top of his skull. 

“When I’m done this mess is over, I’m going to give you such a reward for this, baby.” You whispered, licking at his neck in the spot that you knew made him crazy. 

Sans whined softly, “Is that a promise?” He asked, grabbing onto your shirt and looking up at you. 

You kissed him between the eye sockets. “Yes, it is.” 

You disentangled yourself from Sans and went into the kitchen, finding a vase to put the flowers in. 

“How long will it last?” He asked, perching himself on a chair at the kitchen table. 

“About a week-“ 

“A WEEK?” He shrieked, standing so fast his chair over turned. “Yer gonna bleed for a WEEK?” 

“Yes, Sans.” You tried to sooth him, coming over to him and righting his chair and pushing him back into it. 

“Holy shit,” He muttered, putting his face in his hands. “That’s fucked up.” 

You laughed at this because you agreed. Then you winced, putting a hand against your stomach as a more intense cramp rolled through you. 

“Shit.” He muttered and picked you up, making you squawk in indignation. “Yer hurtin’, __y/n__. Why didn’ ya tell me yer in pain.” He demanded, aggravated. 

“Sans, I’m not. Just a little-“ 

He ignored you as he carried you into the bedroom and deposited you on the bed. 

“Sans!” 

“Just stay in bed, doll.” Sans told you earnestly, laying on top of you and wrapping his arms around you as he rested his chin on your chest and looking up at you with worried eyes. 

“Ain’t got nothin’ big to do today, right? So just stay in bed with me.” 

You let out a sigh and reached up to rub the back of his skull. He purred against you, nuzzling against you chest. 

“For a little while, Sans.”


End file.
